Preheat oven to 325°F / 165°C.
Place silicone heart molds on a rimmed baking sheet (critical for even heat).
In a heat-safe bowl, melt the chocolate and coconut oil until smooth.
Whisk in the nut butter until fully emulsified.
Whisk in the coconut sugar while the mixture is still warm. Let is cool for just few minutes and then Add eggs, egg yolk, and vanilla. Whisk until glossy and smooth.
Sift in cocoa powder, coconut flour, collagen, and salt.
Fold gently until just combined. Do not overmix.
Divide batter evenly between heart molds, filling ¾ full.
Bake 16–20 minutes, rotating the tray once halfway.
Let brownies cool at least 20 minutes before removing from molds.
Silicone releases cleanly only once fully set.